Ion-sensitive field-effect transistors (ISFETs) are chemical sensors that easily determine pH and other related characteristics of solutions. When manufactured using integrated circuit technologies, their performances are quite suitable for automatic measurements such as in FIA systems. However, ISFETs present inherent drawbacks that produce their degradation during their lifetime. In this paper, the on-line determination of this degradation using special electronic devices is presented. The good behaviour of the integrated sensors can be assessed if structures sensitive to the variations of dielectric and packaging quality are fabricated together with the ISFET. © 1993.